Benthic biodiversity in four pairs of Norwegian lakes

The aim of the project was to assess the effect of water-level regulation on diversity of lake littoral meiofauna and protists. Littoral fine-gravel bottoms of four pairs of Norwegian lakes were sampled in June and September 2021. Lakes were sampled in pairs that had similar water-quality but one of which was regulated and the other was unregulated. The bottom material was sampled at 30-40 cm depth, 1-5 m from the shoreline. Six replicate samples from each sampling point was taken by lowering a 25-cm diameter cylinder (12 cm high) to the bottom and 5 spoons of the bottom material from inside the cylinder was transferred to each sample bottle. No macroinvertebrates (size > 1 mm) were observed in the spoons before emptying them to the sample bottles. Water was filtrated out of the bottles using a 10 µm mesh, and then, samples were stored in 96-% ethanol. In total, the dataset contains 101 samples, including 5 control samples and 96 samples from the lakes. Taxonomic composition of bottom-dwelling meiofauna and protists was determined using DNA metabarcoding of the V4 fragment of the 18S rRNA gene. Taxa were identified using the PR2 reference database (protists) and NCBI GenBank nucleotide database (meiofauna). Caution should be exercised when interpreting occurrences of single species, as the DNA metabarcoding and bioinformatics may contain errors. The effect of regulation on species richness and change in community composition (Alpha-diversity) was assessed using mixed effects models.